Spatiotemporal changes in the length and heating degree days of the heating period in Northeast China

As the coolest region in China, Northeast China has long and severe winters and is a main region for the use of central heating. Accurately predicting the heating energy consumption in Northeast China is very important for energy management and planning. Based on daily mean temperature data from 70 weather stations, this study investigated the spatiotemporal changes in the starting date for heating (HS), the end date for heating (HE), and the length (HL) and the heating degree days (HDD) of the heating period in Northeast China. Over Northeast China, regional averaged HS has become later by 0.77 days decade(-1) and HE has become earlier by 1.19 days decade(-1) during 1960-2011. Accordingly, regional averaged HL and HDD decreased significantly by 1.97 days decade(-1) and 66.28 degrees C decade(-1) respectively; this implies a decreasing demand for heating throughout the region. Spatially, the temporal trends of each heating variable varied in different locations. The spatial patterning of the HL trend was unlike that of the HDD trend due to different responses of HL and HDD to climate change. Temperature increase seems to have larger impacts on HL in warm south localities but more obvious effects on HDD in cold north localities of Northeast China. These different sensitivities of HL and HDD to temperature change should be considered when attempts are made to predict heating energy consumption in Northeast China in a changing climate.